Lateral/vertical transistor structures and process of making and using same

Abstract

A microfluidic device can include a base an outer surface of which forms one or more enclosures for containing a fluidic medium. The base can include an array of individually controllable transistor structures each of which can comprise both a lateral transistor and a vertical transistor. The transistor structures can be light activated, and the lateral and vertical transistors can thus be photo transistors. Each transistor structure can be activated to create a temporary electrical connection from a region of the outer surface of the base (and thus fluidic medium in the enclosure) to a common electrical conductor. The temporary electrical connection can induce a localized electrokinetic force generally at the region, which can be sufficiently strong to move a nearby micro-object in the enclosure.

We claim: 
     
       1. A microfluidic device, comprising:
 an enclosure having a microfluidic structure and a base, 
 wherein the base comprises a common electrical conductor, 
 wherein the microfluidic structure and an outer surface of the base together define a flow path within the enclosure, 
 wherein the base comprises an array of transistor structures, each said transistor structure in the array comprising a lateral bipolar transistor connecting a corresponding region of the outer surface of the base to the common conductor, and 
 wherein each said transistor structure in the array further comprises a vertical bipolar transistor connecting the corresponding region of the outer surface of the base. 
 
     
     
       2. The microfluidic device of  claim 1 , wherein each said transistor structure in the array comprises a collector region, a base region, and an emitter region,
 wherein the base region surrounds the emitter region and comprises a lateral portion and a vertical portion, 
 wherein the collector region surrounds the base region and comprises a lateral portion and a vertical portion, and 
 wherein each said transistor structure in the array is physically separated from other transistor structures in the array. 
 
     
     
       3. The microfluidic device of  claim 2 , wherein the lateral portion of the base region has a lateral width that is between about 10 nm about 400 nm. 
     
     
       4. The microfluidic device of  claim 1 , wherein each said transistor structure in the array is physically separated from the other transistor structures in the array by a trench, further comprising an electrically insulative material disposed in the trenches. 
     
     
       5. The microfluidic device of  claim 2 , wherein the lateral portion of the base region has a lateral width that is between about 200 nm and about 300 nm. 
     
     
       6. The microfluidic device of  claim 2 , wherein the vertical portion of the base region has a vertical thickness equal to or greater than the lateral width of the lateral portion of the base region. 
     
     
       7. The microfluidic device of  claim 6 , wherein the vertical thickness of the vertical portion of the base region is about two to four times greater than the lateral width of the lateral portion the base region. 
     
     
       8. The microfluidic device of  claim 2 , wherein the base region comprises a p-type dopant, wherein the collector region comprises an n-type dopant, and wherein the emitter region comprises an n-type dopant. 
     
     
       9. The microfluidic device of  claim 2 , wherein the collector region has a resistivity that is between about 5 ohm-cm and about 10 ohm-cm. 
     
     
       10. The microfluidic device of  claim 1 , wherein the common conductor comprises an N+ semiconductor substrate upon which the array of transistor structures rests. 
     
     
       11. The microfluidic device of  claim 10 , wherein the N+ semiconductor substrate has a resistivity that is between about 0.025 ohm-cm and about 0.050 ohm-cm. 
     
     
       12. The microfluidic device of  claim 2 , wherein the lateral portion of the collector region has a lateral width that is between about 100 nm and about 1000 nm. 
     
     
       13. The microfluidic device of  claim 2 , wherein the lateral portion of the collector region has a vertical thickness equal to or greater than the lateral width of the lateral portion of the collector region. 
     
     
       14. The microfluidic device of  claim 13 , wherein the vertical thickness of the collector region is about two to ten times greater than the lateral width of the collector region. 
     
     
       15. The microfluidic device of  claim 2 , wherein the collector region has a resistivity that is between about 5 ohm-cm and about 10 ohm-cm. 
     
     
       16. The microfluidic device of  claim 2 , wherein a vertical thickness of the emitter region is between about 10 nm and about 500 nm. 
     
     
       17. The microfluidic device of  claim 2 , wherein a vertical thickness of the vertical portion of the base region is about six to twelve times greater than a vertical thickness of the emitter region. 
     
     
       18. The microfluidic device of  claim 2 , wherein a vertical thickness of the vertical portion of the collector region is about three to six times greater than a vertical thickness of the vertical portion of the base region. 
     
     
       19. The microfluidic device of  claim 1 , wherein a pitch of the transistor structures of the array is between about 1000 nm and about 20,000 nm. 
     
     
       20. The microfluidic device of  claim 1 , wherein a pitch of the transistor structures of the array is between about 8000 nm and about 12,000 nm. 
     
     
       21. The microfluidic device of  claim 4 , wherein a vertical depth of the trench is between about 2,000 nm and about 11,000 nm, and a lateral width of the trench is between about 100 nm and about 1000 nm. 
     
     
       22. The microfluidic device of  claim 1 , further comprising a dielectric border disposed on the outer surface of the base between adjacent pairs of the transistor structures of the array. 
     
     
       23. The microfluidic device of  claim 1 , wherein the microfluidic structure and the base together further define a holding pen, wherein the holding pen is connected to the flow path. 
     
     
       24. The microfluidic device of  claim 1 , wherein the flow path comprises a fluidic channel. 
     
     
       25. The microfluidic device of  claim 1 , wherein:
 the transistor structures of the array connect different regions of the outer surface of the base to the common conductor, and 
 the regions of the outer surface of the base are disposed to contact directly fluidic medium in the flow path. 
 
     
     
       26. The microfluidic device of  claim 25  further comprising a biasing electrode, wherein the flow path is disposed between the biasing electrode and the common electrical conductor of the base. 
     
     
       27. The microfluidic device of  claim 1 , wherein:
 the base comprises a first section and a second section electrically insulated from the first section; 
 the array of transistor structures is a first array of said transistor structures in the first section, the base comprising a second array of said transistor structures in the second section; 
 the common conductor is a first common conductor that is common to the transistor structures of the first section but not the transistor structures of the second section; and 
 the base further comprises a second common conductor that is common to the transistor structures of the second section but not the transistor structures of the first section. 
 
     
     
       28. A microfluidic apparatus, comprising:
 a first microfluidic device; and 
 a second microfluidic device, 
 wherein each of the first and second microfluidic devices is configured according to the microfluidic device of  claim 1 , 
 wherein the enclosure of the first microfluidic device is separate and distinct from the enclosure of the second microfluidic device, and 
 wherein the common electrical conductor of the first microfluidic device and the common electrical conductor of the second microfluidic device are electrically connected and compose an electrical conductor common to the first microfluidic device and the second microfluidic device. 
 
     
     
       29. A system which comprises the microfluidic device of  claim 1  and further comprises control equipment for controlling operation of the microfluidic device. 
     
     
       30. The system of  claim 29 , wherein the control equipment is selected from the group comprising a flow controller for controlling a flow of fluidic medium in the flow path, an optical device for capturing images inside the enclosure, and a processor for controlling operation of the microfluidic device.